Scientists working on better design for fishways

Acadia University student Sam Adams records data at a fish passage way at the Sheffield Mills marsh on the Habitant River in Kings County. (GORDON DELANEY / Valley Bureau)

SHEFFIELD MILLS — Scientists are evaluating dozens of fishways in Nova Scotia, with a plan that could see them replaced with better designed structures that can be used by a greater variety of species.

There are currently 160 fishways in Atlantic Canada that were built by Ducks Unlimited. Forty-one of them are located in Nova Scotia, said Geoff Harding, head of major projects for Ducks Unlimited Canada.

They’re all associated with conservation projects and can be found from Yarmouth to Cape Breton. But most are located in the Tantramar Marshes near Amherst, as well as the Annapolis Valley and Truro areas, Harding said in a recent interview.

Many were built about 30 years ago to the Fisheries and Oceans Canada standards of the day.

Called “technical fishways,” the structures are comprised of two parallel concrete walls with a series of baffles that create pools. A notch in the baffles concentrates the flow of the water so the fish can move from one pool to the next.

“They were mainly aimed at trout-like species that have good jumping characteristics,” Harding said. “But DFO is now looking for fishways that allow a greater variety of fish species to successfully get up them.”

“It’s quite complicated to make these things work,” said Harding. “There’s been a lot of research in New England and Europe on the best way to design them so that they work with native species of fish.”

Ducks Unlimited decided a year ago to investigate the application of more natural fishways in Atlantic Canada as the time approaches to replace the existing structures.

Because there is a large research component to the project, the non-profit conservation group has partnered with Acadia University to evaluate the performance of the existing structures in Nova Scotia.

“We built those 41 fishways to DFO specifications,” said Harding. “But we don’t know, and neither does DFO, how well they’re working.”

To monitor the performance of the existing technical fishways, a team of scientists is tagging brook trout and gaspereau with electronic pit tags, tiny transmitters that can track the fish as they move up the ladders.

“They (DFO) want a year of data on these,” Harding said. “The fact that nobody has done much analysis of the performance of existing ones, and the fact that there is a move toward these nature-like fishways, this is something that we’re going to be involved with for the next number of years.”

On Prince Edward Island, Ducks Unlimited is building a natural fishway next to a technical one, with plans to evaluate the performance of one against the other.

“For the next step in Nova Scotia, we have identified some sites where we’re going to take out some technical fishways and start to install the natural, long, gentle-sloped ones,” Harding said.

Sam Andrews and Matt Gregoire are Acadia University students working toward a masters in biology. So far, they have tagged more than 400 fish in four waterways in the Tantramar Marsh area and another 65 in the Habitant River in Kings County.

Once the new ladders are built, the students will continue to tag and record fish passage for at least another two years, said Harding.

“Many of the fishways are 25 to 30 years old and will need to be replaced,” Andrews said in an interview at the Sheffield Mills Marsh, where one of the newest fishways is located.

In addition to tagging brook trout, he has also tagged some suckers and Amercian eel in the Habitant River.

The Fisheries and Oceans Canada is providing $150,000 to the project this year. Irving Oil Ltd. has donated $100,000.